1. Field of the Invention
The present general inventive concept generally relates to an image forming apparatus and a method of supplying power thereof, and more particularly, to an image forming apparatus for preventing an occurrence of an inrush current by a sudden voltage fluctuation which occurs as an open circuit is changed to a short circuit when a mode of the image forming apparatus is changed from a power saving mode to an activation mode, or a state of the image forming apparatus is changed from a turned-off state to a turned-on state, and a method of supplying power thereof.
2. Description of the Related Art
As a part of efforts for environment protection, efforts to reduce energy consumed by electronic devices are proceeding globally. In particular, regulation of electricity consumption of electronic devices in standby mode is being enforced.
For example, an electronic product to be released in a domestic market of the United States, Europe, and Korea should satisfy power the consumption standard of each country (i.e., the Environmental Protection Agency (EPA) Energy Star Product Specification for Imaging Equipment Version 1.2 in the United States, State 2 of the European Commission Ecodesign Directive for Energy-related Products (ErP), and a level below 0.1 W as stated by the Public Procurement Service in Korea).
In order to satisfy the regulations for standby power consumption, technical development to reduce power consumption when an electronic product enters into a standby mode is proceeding. Developments include a method of improving efficiency when a switching mode power supply (SMPS) has a light load, a method of reducing a load of a controller in standby mode, a method of opening a channel connected to a unused load, and the like.
Among the aforementioned methods, a power saving mode refers to a mode where an unused load channel is opened, and minimum power to operate an electronic device is supplied.
With reference to an image forming apparatus as an example, when the image forming apparatus is not used for a predetermined time, the image forming apparatus enters into a power saving mode, and in the power saving mode, minimum power is supplied to a controller configured to determine whether a command from a user has been inputted from outside, and no power is supplied to machines configured to perform operations such as printing, scanning, copying, and the like.
Subsequently, when the mode of the image forming apparatus is changed from the power saving mode to an activation mode, an open state of a load side circuit is changed to a short state, and a large amount of inrush current occurs because of a sudden voltage fluctuation.
To be specific, current (i) may be expressed as a derivative of voltage (V) with respect to time (t) (dV/dt), and thus when a sharp voltage fluctuation occurs in a short period of time, it causes a large amount of inrush current. The inrush current lowers stability of a system by causing stress on circuit components and affecting an output voltage drop of the SMPS.
The aforementioned problems occur not only when the mode of the image forming apparatus is changed from the power saving mode to the activation mode, but also when the state of the image forming apparatus is changed from a turned-off state to a turned-on state.
Hence, there is a need for an image forming apparatus configured to reduce an inrush current of a direct current (DC) output unit and a method of supplying power thereof.